Angiotensin-II plays a central role in mammalian electrolyte homeostasis and blood pressure control (Peach Physiol. Rev 57 313-370 (1977); Vinson et al “The Adrenal Cortex”, Prentice Hall, Englefield Heights (1992)). Two main types of angiotensin-II receptors, designated types 1 and 2 (AT1 and AT2), have been recognised, but the majority of the well known actions of angiotensin-II occur via the AT1 subtype (Herblin et al Am. J. Hypertens. 4 299S-302S (1991); Ouali et al J. Steroid. Biochem. Mol. Biol. 43 271-280 (1992)).
A monoclonal antibody 6313/G2 to the AT1 receptor subtype (Barker et al J. Mol. Endocrinol. 11 241-245 (1993)) has been used to study the distribution of the receptor (Vinson et al Mol. Med. Today 1 35-38 (1995)). The monoclonal antibody has been suggested for use as a therapeutic agent to control vaso-constriction, for example in the treatment of hypertension or uterine contractions.
The antibody has been used as a specific imaging agent in various tissues, for example laryngeal cancer (Marsigliante et al Cancer Letters 110 19-27 (1996)), kidney (Harrison-Bernard et al Am. J. Physiol. 42 F170-F177 (1997); Cheng et al Am. J. Physiol. 43 F10-F17 (1998)), and brain (Yang et al J. Neuroscience 17 1660-1669 (1997)). The antibody has been shown to block angiotensin-II induced AT1 receptor internalisation and PKC activation but conversely promotes the calcium response (Kapas et al Biochem. Biophys. Res. Comm. 204 1292-1298 (1994; Vinson et al J. Endocrinol. 141 R5-R9 (1994)). The presence of AT1 and At2 receptors in breast tumours has been reported with local production of angiotensin (Inwang et al Brit. J. Cancer 75 1279-1283 (1997); Tahmasebi et al Eur. J. Cancer 34 1777-1782 (1998)).
Monoclonal antibody 6313/G2 is secreted by a hybridoma cell line deposited on 21 Jul. 1993 with the European Collection of Animal Cell Cultures (ECACC), Porton Down, United Kingdom, under the Budapest Treaty, and designated by the accession no. 93072117. The deposit was made by Dr Gavin P Vinson and Dr Stewart Barker, Department of Biochemistry, Queen Mary & Westfield College, Mile End Road, London E1 4NS. The depositor has authorised the applicant to refer to the deposited material in the application and has given his unreserved and irrevocable consent to the deposited material being made available to the public in accordance with Rule 28(1)(d) of the European Patent Convention.
The hybridoma cell line produces an antibody that specifically binds to amino acid residues 8 to 17 of the rat vascular smooth muscle AT1 receptor, which sequence is also found in the AT1 receptor of human and bovine cells. The epitope sequence is as follows:                EDGIKRIQDD (SEQ ID NO:2)Or, alternatively expressed as,        NH2-Glu-Asp-Gly-Ile-Lys-Arg-Ile-Gln-Asp-Asp-COOH        
It has now been surprisingly found that monoclonal antibodies to the peptide sequence comprising the N-terminal sequence of the angiotensin-II type-1 receptor have additional therapeutic uses in certain medical conditions where such uses were not previously suggested or shown. Furthermore, these therapeutic effects are seen in the ability of the monoclonal antibodies to block the harmful actions of angiotensin-II in the medical conditions concerned whilst preserving the beneficial actions of the molecule. A functionally important role for the entire N-terminal sequence has now been realised.